1. Field of the Invention
The present invention relates to an automatic flash amount control apparatus of camera, which meters a flash amount upon flashing with a photographic field being divided into a plurality of regions and which controls a flash amount in accordance with the result of metering.
2. Related Background Art
An automatic flash amount control apparatus of this type is for example as described in Japanese Patent Application No. 3-160140 filed by Applicant. This apparatus has electronic flash means capable of performing preliminary flash and main flash, in which segmental metering regions are used for metering of reflection light from a photographic field upon preliminary flash and in which control regions to contribute to a flash amount control upon main flash are determined based on focus detection information and the focusing mode. The flash amount control is carried out upon main flash, based on signals of metering in the thus determined control regions.
The automatic flash amount control apparatus, however, determines a metering region overlapping with a focus detection zone as a control target region when a focus detection device detects an in-focus state. If the focus detection device erroneously detects the in-focus state in that arrangement, proper exposure cannot be set in flash amount control, which was a problem to be solved.
Especially, in case that a photographic lens has a short focal length, the depth becomes shallower to decrease the focus detection accuracy, which may cause such a problem. For example, when the composition is shifted after the focus is set and locked on a main subject, the focus detection device is naturally to output a judgement of out-of-focus with respect to the background, though the photographic distance is fit to the main subject. However, if the photographic lens has a short focal length, it is not rare that the focus detection apparatus outputs a judgement of in-focus with respect to the background even in change of composition.
Another automatic flash amount control apparatus is for example as described in Japanese Patent Application No. 2-312487 filed by Applicant. This apparatus has electronic flash means capable of performing preliminary flash and main flash, in which segmental metering regions are used for metering of reflection light from a photographic field upon preliminary flash, in which the plural metering regions are separated into effective regions and noneffective regions, based on metering values and a photographic distance, and in which the main flash is controlled using the effective regions.
The automatic flash amount control apparatus, however, detects the photographic distance as a long distance corresponding to the background, if a focus detection device erroneously effects focusing on the background behind a main subject. If the separation between effective regions and noneffective regions is carried out using the long photographic distance, proper exposure cannot be set, which was another problem.
For example, since the main subject is considerably closer to the camera as compared with the detected photographic distance in the above case, the camera judges that reflection light from the main subject is too much, whereby the region is set as a noneffective region. Then, the flash amount control is effected upon main flash with target regions where the main subject is absent, resulting in obtaining an excessively over-exposed picture.
In addition to the focusing through the focus detection device, the photographic distance may be determined by manually moving to set a distance ring of photographic lens based on estimation with eye and detecting the position of lens by an encoder. The same problem could occur in that case.